Tire rotation is a non issue for a correctly outfitted Vette!

Real tires are direction rolling and different size from front to back

My grandmother can rotate her tires

 

I have run close to maximum tire pressure for many years now after I attended a Skip barber racing driving school in the early 90's when they were using Michelin tires. The Michelin tire rep who spoke to the group one day said that all tire manufacturers make their tires to run at much higher pressures (the tire pressure designation) but the car manufacturers specify tire pressure in the door jam that is a compromise between ride, handling, and wear. According to Michelin, the pressure you may want to run for maximum grip, handling and wear is the most that you the driver can tolerate (ride quality) below the specified tires pressure designation on the sidewall, not the car door jam. Running maximum tire pressure does necessitate mandatory tire rotation for even wear though. My first set of tires that I tried running high pressures on were a 1992 Chevy Lumina with Goodyear Eagle GT + 4's that were Z rated (notorious for poor wear). At 50,000 miles on those tire, the tires were worn on the wear bars and the goodyear service center that serviced the car (company car), told me he had never seen that tire go 50,000 miles - lots of tire pressure!!

 

Front to back??? I have not done what you said in about 20 years or so......

How many folks on here are running different size tires on thier c3? I don't believe there are many, But I have been wrong before.

 

I run what the tire sidewall says in all my vehicles.

 

And yet IMOE the Michelin engineers for the ProSeries (who regularly compared data with that of mine) seemed baffled that their relatively high recommended cold pressures didn't often result in optimum temps for their racing slicks purpose-built for those specific Reynard chassis. IIRC, pretty much all of us started a few pounds below their pet numbers to actually optimize the contact patches once the tires came up to temp. While it might indeed work out in some instances, strictly going by max cold pressures as stamped on the sidewall simply does not, can not guarantee proper inflation in every case, any more so than strictly adhering to door jamb numbers.

 

Using max cold inflation is virtually always going to result in a tire that "crowns" at operating temperature, giving a reduced contact patch.

That said, with a few exceptions my autocross testing across many different vehicles typically indicated a pressure of about 3-5 PSI higher than specified by the vehicle manufacturer. If you don't think a PSI or 2 makes a difference, then it's time for you to head to a local autocross!

If you're going to run this reduced patch,then certainly regular rotation is key - the fronts will be OK due to the roll to the edges, but the rears will wear in the center. But far better to optimize the contact patch by investing a little time and money - as TSW noted, the cheaper IR meters are good enough for a street car, but the additional cash for the probe type is well-spent. Mine gets borrowed constantly

If you're worried about tire wear and ride comfort, might I suggest a nice Prius?

 

I did not mean to imply that you should run the max pressure on the sidewall but a pressure something less than the max pressure and the factory recommendation. I have been running much higher pressures for 20 years on cars of all types including my C3 with excellent results on the street. Granted finding the right pressure is different for every vehicle and involves a little bit of an art and trial and error. For example, I run about 36-38 PSI on my C3's 255/45/50/17 ZRs, 40 PSI out of 44 Max on the 1994 Mustang GT, 40 out of 44 max on the 245/55/18's on my 300 etc. Running significantly higher pressures than the factory recommendation will drastically increase tire life, improve handling and steering response, require tire rotation, slight ride quality degradation and could result in some uneven tire wear although that has never been a significant problem with my cars over the years. The aforementioned early Goodyear GT+4's Z rated achieved incredible mileage (50,000 miles) but did have some crowning running 44 PSI max pressure. My experience in general has been that to achieve significant results on the street you will need to increase the tire pressure significantly-anywhere from 8-10 PSI if the factory recommendation is 28 PSI, to 4-6 PSI, at least, if the factory recommendation is 32 PSI, maybe 5 PSI in general again, if the factory recommendation is 35 PSI. Where tires are concerned, there is no free ride-everything is a compromise. There are big improvements by using the best tires for our C3's and significant improvements from adjusting tire pressure.

I do run different tires on my C3 and it was one of the biggest factors in improving the overall drivability of the car:

255/45/17 ZR front/255/50/17 ZR rear:

 

My observation is still that there's no "art" or trial and error to it, specifically in terms of maximizing the contact patch. SOTP means nothing here, no more than timing an engine by ear.

 

Take a can of marking paint and paint a stripe of across the tread of your tires. Drive it a little ways. Get out and check what the wear pattern looks like. If the paint is gone from the center, remove some air. If it's missing from the shoulders, add air. Trial and error, but it works.

I'm a former goodyear franchise owner and got this right from the proverbial horse's mouth.

 

Using a stripe across the tread is better than SOTP and will get into the ballpark, but is still not particularly accurate. I started in autocross using white shoe polish both on the sidewalls and across the bottom, looking both at sidewall rollover and contact patch. Then I got turned onto a pyro.

What I found was that high performance tires - maybe not Grandma's Honda Accord tires - varied dramatically once they were fully at temperature...and of course they don't stay at temp very long after you stop. The stripe across the tread wears off pretty quickly, and things have to be pretty far out of whack before you get a clear indication of over/under pressure, especially on the front tires that are often experiencing some level of "scrub" under hard cornering.

If close enough is good enough, then it's fine. If you really want to get the most possible traction out of the tire, borrow or spend the $$$ on a pyro. I spent something like $600 on my TIF, the new ones are < $200 for a decent one, about double that for a pro level.

'nuff said by me, I think at this point I'm

 

Chalk is OK but I use 8 x 11 copy paper. Spray 4 sheets with Windex (water works but for some reason Windex works better) and let the excess drip off. I pull my car into the garage smooth concrete floor and place a sheet under each tire. I don't start the vehicle because fan or exhaust may shift the paper. Push the vehicle over the paper one time and you will get a perfect imprint. Do it a few times with new paper each time and you will see the results are consistent. You will also notice if the imprint favors one side or the other. Try it out and let me know if it works for you. My 69 came with bias ply tires, now I have radials and inflation is the key. By the way, factory inflation is 24 lbs for my 69.

 

Ummm...this is with the tires cold?

Can't see how that tells you anything about the tires hot...which they always will be when running.

 

It'll tell you what your camber settings are, kind of.

Everything you said above was spot on, I'd just want to add that they should be using a NEEDLE pyrometer, not an IR gun, otherwise you may get an average reading of nearby surfaces.

 

Read back - I suggested the probe type previously...but recognizing the price point the IR gun is still better than guessing

 

My bad. I did a search for "needle" and came up blank and didn't read all the way back.

 

Ummm...this is with the tires cold?

Can't see how that tells you anything about the tires hot...which they always will be when running.


I did it after a run so tires were hot.

 

Tires cool from operating temps in a few minutes at most...so again, I can't see this approach delivering valid results. How about posting some pics of the results of this process, along with the pressures?

 

I'm continually amazed whenever the topic of tire pressures comes up by how often the science of tire temp data is ignored in favor of guesstimation based on the most crude of methods. Come on people, this is the 21st century already!

FWIW, tires temps cool and/or even out substantially within less than a few minutes, so get those temps recorded ASAP while they're hot.